Production of 2,3-dimethylbutadiene-1,3



Patented Apr. 15, 1947 umrro fi sr res -PATE;NT om-cr Julian A. tto,.Lon g Island-flitiNr exand-Albert .E. Anderson, Danielson, Gonna :assignors to General Chemical Company, New York, N. X a corporation of Ne'wYork :NozDrawing: ApplicationMay 1, 1945, .Serial No. 592.528.

This, invention vrelates .to, the production :of

:2,3-dlmethy1butadiene-L3 by dehydration". of-

,pinacol.

2,3-.-.dimethylbutadiene-1,3 is a .diolefin which is potentially of considerable industrial impor. $51108 :as a starting material for production of synthetic plastics, particularly synthetic rubber, :bypolymerizatlonand.copolymerization. Various methodshave been proposediheretofore for form- .ing this dimethylbutadiene by dehydration .of pinacol; for examplefit has been proposed ,toheat sninacollin the liquid phase in the presence of hydrobromic acid, whereupon a portion of the pinacol slowly is dehydrated to form .dime'thylibutadiene which is removed as distillate. Iti has also been proposed to dehydrate p'inacol tedimethylbutad'iene in the vapor phase'by passin pinacol vapor'in' contact with aluminum oxide at temperatures. approaching 500 C.,; this particular dehyizlra'tion, .as described (in the rior art, has

been carried outon only a laboratory scale and pyrex tubes have generally been employed as the catalyst chamben 'Inthe prior art descriptions of other vapor phase dehydrations of alcohols to olefins, only iron, .stee1,.or stainless steel have been suggested as ,ajsubstitute for commercially impractical glass or' quartz. Such suggestions are found, for-example, in-Un-ited-States Patents 2,237,866 of April B,194'1, 2;224,9'12 of December '17, I940, and 2,345,113 of March '28, 1944.

Attempts to place the vapor phaseprocess'for producing 2,3-dimethylbutadiene lfi by catalytic dehydration of pinacol into commercial operation have been discouraging became when itha-s been attempted to use more practicalmaterials than glass as the material oiconstruction for the catalyst chamber, egg-materials such as the steel or stainless steel suggested in the .abloye patents relating to dehydrations of other. alco- '?ho,ls, it has been found thatjyields .Ofif 2,3-dianethylbutadiene--l,-3 "have become unaccountably erratic. It :can only be ec'onc'lude'd that this is clue to an adverse catalytic efiect of the surface 'n'f ithe steelor stainless steel chamber. Glas yessel .are. "undesirable "for fuse on .a .large' scale because of low heat conductivity and fragility; other materials, such as brass or copper, that might be considered as construction materials corrode unduly either during the reaction or during subsequent bloWing of the catalyst cham-' her with air for catalyst reactivation.

An object of this invention is to provide a satisfactory large scale process whereby 2,3-dimethylbutadiene-1,3 may be produced from pinacol in excellent yields.

' 7 :We have now discovered that although materials such 28S steel or .stainless steel, which one would expect to be inert to the reactants and 'reactioniil roducts present-in the vapor phase dehydration of pinacol to 2,,3-dimethy1butadienfi- 1:3 over an aluminum .oxide catalyst, interfere with the dehydration -or catalyze side reactions to such .an extent as to make :the process un- EattractiMe commercially, there is one class ofcon- .struction materials, namely non-ferrous metals comprising redominantlynnickel, .e. g. nickel, :Moncl metal or rnichrome, that surprisingly does .not interfere with the vapor phase dehydration }process. We have found that high yields of 2.3- dimethylbutadiene-L3 may .be maintained over 'a .long period of time by carrying out the vapor phase dehydration of pinacol .o er an aluminum oxide vcatalyst contained in a chamber made .or lined with .a .non-ferrous metal comprising pra. dominantly nickel, so that the reactants, while a .reaction temperature, are .in contact with the :llOlhfQll-QHS vmetalsurface, but not in contact with a sub'stantial amount of v.a ferrous metal.

.In'carryingout the process of ourinvention, an aliuninum .oxide which has heen round suitable fior' use; as -tcatalyst 'is the activated alumina, grade .F-l, of the Aluminum Ore Company; this grade of alumina has an A1203 content of about 92.0%. The alumina is preferably employed in lumps ranging Irom .4 to 18 mesh. In accord- -.ance with the process .of our invention the lumps ferrous .metal comprising predominantly nickel or rnay .be-rnade of ordinary. steel lined with. such non-ferrous .metal at all points where .vapors ,or pinacol at high temperatures will contact the catalyst chamber; Monel metal, i. e. .thealloy .clon- :tainin'gabout 5.1% .nickeLtabcut .30%fccnner and 40 amcunts 10f, JronQsilicon, carbon and manganese, is preferably employed, jbut nickel -..or nichromes, i. e. thcse alloys the principal-constituents or which are nickel, chromium and iron lngpropontions of about .54;%..to.8 0% nickel, 10% to"-20-% chromium and 7% to 27% iron, may also "beemployed'."

, Lmih'ydrous pinacol (which may be prepared. 233 p acol lhrdrate'by preliminary distillation) Jscnntinuously ranorized .tcobtain a stream of 150 pinacol vapor.

absolute (the preferred pressures for carrying out ofraluminaare packed'intoalcatalyst chamber 7 ich-may be constructed entirely or .a .nc

the dehydration), the pinacol is vaporized at a substantially lower temperature, e. g. 85 to 130 C.

The pinacol vapor is passed into the abovedescribed catalyst chamber packed with alumi-' 5 num oxide" and maintained at a temperature-in the neighborhood of'about 400 to500" C.-, preferably 420 to 480 0., wherein it is largely de hydrated to form 2,3-dimethylbutadiene-1,3 and water. The gaseous reaction product is passed it} through a partial condenser, preferably maintained at a temperature in the rangeof about to --20 0., to remove water, unrealcted"pi1ie .cc' l,"- and'possibly small amountsof.liquidby products such as pinacoline and isopropyl-"alcohol'; '-'-Ihe 1 gas which passes out of this partial condenser contains the desired 2,3-dimethylbutadiened,3

product. This product is liquified by passing'ituii through a condenser maintained at -.;60. to... 800 C i Aiter operation for a period of time, usually ranging from 5 to 7 hours, it 'is" desirable to refa'ctivate thealuminurn oxide catalyst." This'i's 'a'ccomp'lished by passing air through thecatalyst chamber at a temperature'generally'above 420 C; and ranging up to as high as 650C. When "air ihasthus been passed through'the catalyst ch arn 'er'forabout 6 hoursft'he catalyst is rea'dy'foi' "reuse for dehydration of further pinacol. Ii1-thefollowing example, illustrative ofthe process of our invention, the marked difference jin yigld of the dimethylbutadiene whichfisfobtained employing steel, on the one hand, and "Monel metal, on the other hand, as the material :of' construction 'for the catalyst'chamberIis Q19 Yd 1 i Q i Exemplar-Catalyst chambersywere, prepared jfromsteeland from Monel metal for twdparallel runs on vapor phase dehydration of pinacol.f In jeach= case, the catalyst chamber wasin tubular forrn. The steel employed'was of the type-known jcommercially as medium steel, containing'0I25% "0.60% ,carbon. The Monel metal containedj'67% r ickel," copper and traces of iron, s il icon,

manganese and carbon; Each ofv these 'catalyst 4:5 chambers was packed with 48 'mesh aluminum 1 oxide of the type known commercially asfhctiva'ted Alumina, GradeF-l, made byv Aluminum O re .Cqmpan a 1 1' Pinacol' vapor prepared by vaporiaation ofan- ,h ydljolls' pinacol was passed through-each or these l catalyst chambers underan absolute pressure 'fof mm. of mercuryyand the catalyst'chamberin ach, case was maintained at substantially the e temperature, ranging'from420" to 'j480 f- C. 5 I dimethylbutadiene-lfi was recovered from I he product of the dehydration reaction-as de ribed-1:? j i Dehydration was thus continued foraiiumb'er of'hoursand the overall conversion of pinac'olto 4 shown inthefollowing tabulation:

v atthese' high temperatures.

Number dimethylbutadiene resulting from each lfllllj is' 2.419,oso

4 The aluminum oxide catalyst. in each case, was thereafter reactivated by passing air through the catalyst chamber at temperatures ranging from 420? to 650 C. The air had no serious adverse effect on the material of either catalyst chamber Since certain changes may be made in' carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall .be interpreted as illustrative and not in a limiting sense. i

We claim;

:pinacol v to.2,3-dimethylbutadiene-1,3, at tempera,-

tures in the neighborhood of 400 to 500 Q., 'the improvementv which comprises maintaining the reactants at said elevated temperatures incon {tact with reaction chamber surfaces made of a non-ferrous, metal comprising predominantly nickel.

3. .In the catalytic vapor phase dehydration otf .Ipinacolj to 2,3-dimethylbutadiene 1,3, the im- Drovement which comprises passing pinacol vapor over an aluminum oxide catalyst contained within j a chamber having its inner surface made of Monel metal, at a temperature in theneighborihoodof 400 to 500C,

, 4. In the catalytic vapor phasedehydration of fpinacol to 2,3-dimethy1butadiene-1,3."the steps 'that comprise passing pinacol vapor over an', aluminum oxide catalyst contained withina 'cham ber having itslnner surface made of Monel metal, at a temperature in the neighborhood of 400 to 500 C., and after the activity of the catalYSt has decreased -,reactivating said catalyst by passage of air incontact therewith'ata temperaturein theneighborhood of 420 to 650 C.

JULIAN A. OTT O, ALBERT E. ANDERSON.

, REFERENCES CITED. 5 I v The, following references are of record in the =-iile of this patent:

UNITED STATESPATENTS g 7 Date Name I I 2,215,950 Young Sept. 24, 1940 2,272,711 Hull Feb, 10, 1942 FOREIGN PATENTS I v Number Country Date 137,389 Swiss Mar. 17,1930

British June 19, 1943 OTHER'REFERENCES -Talalay et al., Rubber Chemistry and Techno'1ogy,vol. 15, 403-429 (1942); pages 40943. ,423, 424 and 429, especially pertinent. iDiv. 38.)

(Copy in 

